Metal tubing used in heat exchangers is prone to exhibit corrosion over time. To address this problem, some commercially available forms of tubing are made from a zincated microport extrusion. In this process, the microport tubes are usually sprayed with pure zinc as the tubes exit the extrusion press. However, the coverage of the tubes with zinc can be inconsistent and the tubes are expensive to produce. Furthermore, these extrusions can exhibit low strength in the post braze condition. Alternative alloys for use in preparing the tubing are desirable.
The long life (LL) core alloy is known in the prior art and is disclosed in U.S. Pat. No. 6,019,939. This LL core alloy contains the following elements, all expressed in weight percent (wt %): not more than 0.15% Si; not more than 0.4% Fe; up to 0.1% Ti; 0.5-1.0% Cu; 0.7-1.5% Mn; up to 0.8% Mg; up to 0.3% V and/or up to 0.3% Cr. Studies have shown that the LL core alloy disclosed in U.S. Pat. No. 6,019,939 suffers from perforation and failure after 3 weeks in accelerated airside corrosion tests. Thus, there is a need for a brazing sheet core alloy with high strength, corrosion resistance and scrap metal absorbing tolerance for use in heat exchanger applications, for example automotive heat exchangers. The use of more alternative metals containing Fe and Si in the input metal for formation of the alloy can reduce cost and increase recycling capacity.